


Learning restraint

by Lonliest_muffin



Category: Katekyou Hitman Reborn!
Genre: Crying, Domestic Fluff, Dying Will Flames (Katekyou Hitman Reborn!), Flame Harmonization (Katekyou Hitman Reborn!), Fluff and Hurt/Comfort, Hibari Kyoya and Rokudou Mukuro as unlikely friends, Hugs, M/M, Multi, Non-Sexual Bondage, Non-Sexual Intimacy, Polyamory, Starring: Rokudou Mukuro as the voice of reason, Vulnerability
Language: English
Status: Completed
Published: 2020-08-08
Updated: 2020-08-08
Packaged: 2021-03-05 20:15:20
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,081
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25781209
Author URL: https://archiveofourown.org/users/Lonliest_muffin/pseuds/Lonliest_muffin
Summary: Something is going on with his Cloud and his Mist. What could it be?It is absolutely not what Tsuna expected, but this is somehow nice in a weird way.Or, None of this mess may have ever been Tsuna's fault, but he still wants to take responsibility.
Relationships: Hibari Kyouya/Rokudou Mukuro/Sawada Tsunayoshi
Comments: 2
Kudos: 75





	Learning restraint

**Author's Note:**

> I had this idea for a while now and I wanted to just finish one of my things, so I wrote the whole of it in a few hours and here we are!

His Cloud and Mist are unhappy. Well, Kyoya rarely ever seems to be happy and Mukuro is a mystery regardless of his mood. But Tsuna still noticed that, as of late, both of them seem to be... Well, not exactly struggling with something? More so... dealing with something too big for themselves.  
Its fairly obvious to Tsuna, even without the alarms going of thanks to his hyper intuition. It's noticeable in their flames that something is happening, which is a surprise, since the Cloud and Mist flames at the very edges of his bonds are usually more closed off.  
But Tsuna noticed mostly because both his guardians have been avoiding him like the plague. He can't find Mukuro, at all, which is worrying enough already. But then, Kyoya is avoiding him too. Usually, his Cloud tends to just disappear however he pleases for a few days every month anyway, but just yesterday, Tsuna ran into the man in the hallway and Kyoya gave him this strange look before leaving without even a greeting. 

So Tsuna has come to the decision to confront them about it. Preferably before Reborn notices and throws Tsuna into another bizarre bonding experience. Dear God, help him. 

Surprisingly, once Tsuna actually goes to find his wayward guardians, it's easy enough. They're on Kyoya's side of the Headquarters. To be specific, in Kyoya's bedroom. Together.  
But there aren't any crashes coming from inside the room where Tsuna senses their flames the strongest, so he tries not to think about the medical bills and collateral damages these two tend to rake up when they're in a room together.  
Politeness is key on this side of the Vongola HQ, so Tsuna knocks on the door firmly, not quite knowing what to expect.  
Kyoya at least sounds calm when his voice rings out clearly. "Come in." 

So Tsuna opens the door and comes in, promptly freezing up at the situation he ends up seeing. Kyoya is sitting there, by his heated kotatsu as per usual, sipping some tea by the looks of it. The shock comes from the fact that Mukuro is sitting opposite of him, legs put under the kotatsu and slumped over the tabletop, his face buried in his arms there, apparently content to just enjoy the warmth provided by the traditional table.  
Tsuna can't find his voice for a moment, and Kyoya is drinking tea, so Mukuro ends up being the first to speak, staying on the table, but turning his head to face Tsuna and give him a pleased smirk. "Oya, Oya, you came here on your own after all." 

Kyoya puts down his teacup with a little huff and a roll of his eyes. "I told you so."   
Mukuro puts his attention back to the man opposite of him, humming faintly. "You sure did, Skylark. Now what?"   
Kyoya gives a soft, resigned sigh, before he pins Tsuna with his sharp eyes. "Come over here, omnivore. And sit."   
It was an order, so Tsuna immediately does as he was told, sitting on the nearest available pillow and looking at them both. He's still somewhat speechless, but his guardians just go back to whatever they were doing before. 

Meaning, Kyoya is staring down at his tea cup with a tiny frown on his lips and Mukuro starts to faintly hum from where he's face planted into the table. It's painfully awkward. Tsuna actually squirms under the tension that fills the room.   
It all snaps at once when Mukuro speaks again, his voice a little muffled cause he's still buried in his arms against the table. "So do we just tell him? Or do you have something planned?"   
Kyoya huffs again, annoyed, but not angry. "I'm searching the right words."   
Mukuro sighs in a very exaggerated, theatrical manner. "So we're gonna sit here for ages then~"   
It makes Kyoya bristle up a bit defensively, frowning more now, but making no move to grab his tonfa or another weapon. The muscles of his hand do twitch around his teacup and Tsuna is briefly entranced by that movement.

Then the Cloud looks at him and Tsuna is trapped in the intensity in those eyes. "The pineapple and I might require your... Assistance, Tsunayoshi."   
Tsuna can only blink rapidly and make a confused noise after that odd declaration, before Mukuro clarifies with a giggle. "Kufufu... He's saying we need your help, bunny."  
At that, Tsuna's eyes go big, his mouth gaping like a fish for a moment, before he finds his voice again. "You... Need my help? What? How would I..." 

Kyoya stands up abruptly then, making Tsuna flinch hard, but Kyoya just... walks to the side, his arms crossed tightly. Kyoya starts pacing the room, restless, still searching the words. Mukuro lifts his head a bit to observe his pacing rival, before turning to Tsuna again. He isn't smiling and the seriousness in his eyes is unnerving. "You remember the mission you send us on last month? Something about setting an... Example if I remember correctly."  
Tsuna is drawing up blanks, but Kyoya helpfully chips in with his own opinion. "It was the mission concerning the boss of the Volpi familgia. It was successful, of course."

Ah, Tsuna remembers that mission, the clean up was particularly difficult to organize, because the entire mansion's integrity had been compromised by one or two explosions and a rampaging Cloud hedgehog. He nods slowly then, before Mukuro calmly continues. "Yeah, about that. The Skylark actually almost died."  
Kyoya promptly glared at the Mist. "Only because you are too stupid to dodge bullets."  
Mukuro just chuckles in response, putting his head back on the table, cuddling comfortably back into his arms. Tsuna is just left reeling with that information. Something furious and protective flares up in his flame. "Why wasn't I informed of that?!"

Both guardians pause to look at him, Mukuro with amusement, Kyoya clearly taking offense. "It's just a bullet wound, omnivore, I took it easy for a few days and it healed fine."   
Tsuna can't make sense of anything that's going on. His two most difficult guardians are as frustrating as ever. "You-that's-I just-"   
But Kyoya waves one hand dismissively, bulldozing over Tsuna's stuttered protest. "Anyway, that is nothing you can help with. The issues is..."   
The ravenette ends up frowning darkly and Mukuro sighs mildly, just half as theatrical as he could be.

Mukuro looks at Tsuna then, resting his chin in one of his palms, probing his arm up on the table by his elbow. Tsuna can't read what he is feeling from his expression, it's distressing. "So the Skylark got shot and... Reacted accordingly."   
Kyoya huffs, crossing his arms again, frowning of to the side. "I believe I simply obliterated the place."   
Mukuro shakes his head, sighing softly. Now Tsuna can pinpoint the emotion. Sadness with a hint of worry. What. "You did. But you weren't calming down afterwards. And you were bleeding out your guts already, I didn't wanna injure you further. Everyone would've really thrown a fit if I'd killed you on a minor mission like that."   
Kyoya relaxes minutely, sighing softly then, just looking defeated now. "The pineapple had to restrain me so I wouldn't injure myself in my rage. I didn't take that well."

Tsuna blinks rapidly, still a little caught of guard with the emotions displayed by his most terrifying guardians. Mukuro raises one hand, trying to bring up his usual theatrics, but it's a sad attempt, not even Tsuna is fooled. He seems to be really affected by this... "So I wrapped him up in illusionary vines and kept him in place. Then, the Skylark burst into Cloud flames and cried."  
That exclamation is so far removed from the picture Tsuna has of the former prefect, he is actually getting mental whiplash. But Kyoya isn't denying the accusation. He's just... standing there, with his arms crossed, looking over to the gardens. There's a faint, embarrassed flush on his cheeks and he's frowning so...  
Tsuna can only assume he's been booted to some kind of weird parallel universe where everything's upside down and backwards. 

But.... Parallel universe or not, these are his guardians. And he wants to help. "What can I do to help?"   
Mukuro blinks, as if just remembering Tsuna is there, then he shrugs mildly, looking over to the aloof cloud. He wasn't even trying for a smile anymore. "... We started talking a day or two after that all happened. Apparently, it's been happening since he was a kid."  
Kyoya speaks for the first time in a while, soft, but firm. "I do not like to be caged, or restrained. That is all."  
That does trigger something Tsuna is more used to. Mukuro frowns, almost scowling in annoyance. "And that sort of visceral reaction is not normal!"   
Kyoya turns a sharp glare on him, tension rising rapidly, so Tsuna hurries to get his words out before these two start to tear into each other again. "I want to help! How can I help!?"

Fortunately, that makes Kyoya pause and settle back, blinking mildly then. Even Mukuro relaxes significantly, thinking it over. Now Mukuro has trouble finding the right words. "We've been... Trying to... train that... reaction out of him."  
Kyoya comes back to the table, dropping down, unfairly graceful as per usual, but he's avoiding eye contact. This can't be easy to talk about... "In the past, it used to be worse. When I was a very young child, I would end up reacting that way whenever anyone touched me at all."

Tsuna's heart aches in sympathy. And... Something else aches in him as well. Protectiveness. Raw and potent. Because his most powerful guardian, the strongest, most aloof man Tsuna has ever known, is being vulnerable with him. Kyoya continues talking, his voice even and his posture relaxed. Nothing visually betrays the intensity and tension trapped in his eyes. "I trained that reaction out off myself back then through simple exposure. For an example, I would just touch an herbivore's arm or head to check for permanent damages after I'd beaten them unconscious. It stopped inducing that discomfort quite so vividly after a while."  
Tsuna looks down, wondering how he would ever be able to help, but Mukuro speaks again, a small smile on his face. Playful. "Training that out of him means I gotta restrain him well past his comfort levels. It's been fun. But his flame reacts about as violently as you'd guess... Well, that's where you'll come in, bunny boss."

Tsuna's eyes widen, blinking rapidly. "What."   
Kyoya rolls his eyes and Mukuro grins at him. "You are gonna be the one to keep the Skylark's flames in check."   
"What?!"  
Kyoya huffs at him, annoyed. "We'll need to harmonize while I'm restrained. It's simple."   
"WHAT?!"

~~~~~~~

That is how Tsuna ended up in his current predicament, sitting in a high security private chamber, together with his two still most terrifying guardians. They were all dressed in casual wear, since Kyoya insists on not being held responsible if he ends up tearing them and their clothes to pieces. Mukuro sees the whole thing with great humor, chuckling when Tsuna blushes furiously at seeing the two of them.   
Well, Kyoya and Mukuro are unfairly attractive, especially in something simple and humbling like plain t-shirts and swetapants. It makes them look more approachable, which doesn't say much, since usually, they are scary enough to just run away from.   
Tsuna calms his racing heart, grabbing onto his resolve and steeling himself. He is here to help, nothing more, nothing less. 

.... Mukuro looks kind of cute when he giggles like that without his sinister smirk....  
Wait-no-focus! Kyoya is talking! "Ah, it probably doesn't need to be said, but if you tell anyone of anything you have or will hear or see today, I will bite you to death in the most painful ways I can imagine."  
Tsuna shrinks a little, trembling, but nodding his agreement. Vulnerable or not, Kyoya is scary!   
Mukuro just chuckles, amused more than anything. Then, his expression smoothens out, becomes even and neutral. Kyoya looks away from them again, clearly uncomfortable. 

Silence reings for a moment, alongside tension. Anticipation, or maybe dread make the air heavy and difficult to breathe. Tsuna almost gets woozy from lack of air, but the feeling dissipates when Kyoya looks towards Mukuro and nods lightly, giving his consent.   
Mukuro's expression remains neutral, his trident appearing in his hands as he summons familiar lotus vines.   
Mukuro speaks while he manipulates the vines, to get Kyoya to focus his attention on him and not the vines slowly wrapping loosely around his legs. "As per usual, we'll only go until you either start hyperventilating, or breaking stuff."   
Kyoya narrows his eyes at them both, nodding faintly, then closing his eyes and releasing a soft breath. 

The vines are real illusions, Tsuna can sense that much, so they have an easy time wrapping around the Cloud's relaxed arms and shoulders, pulling Kyoya gently to lower him to the ground. Kyoya has to kneel and sit willingly, or that wouldn't have worked.   
Kyoya ends up sitting cross legged on the floor, with vines wrapped loosely around his torso, legs, arms and even some looping somewhat threatening around his throat. Those ones move up to his head after a moment of consideration from Mukuro, settling against Kyoya's forehead. Kyoya is already frowning, clearly unhappy.   
Then the vines go taunt abruptly, not quite cutting into the Cloud, but...immobilising him well enough.

The reaction is instantaneous. Cloud flames fill the room immediately, thick and unhappy, unwavering as they bear down onto both, Mukuro and Tsuna with all their might. And there is a lot of might there.   
They both have to push their own flames against the wall of displeased cloud with their full force, just so they would not end up suffocated or worse, squashed into the floor indiscriminately. Tsuna even has to close his eyes in concentration, shuddering against the sheer force of will radiating of the restrained Cloud.   
Mukuro releases a low sigh, addressing Tsuna with that strange, sad worry in his voice again. "See the problem?" 

Tsuna can only mutely nod, breathing slow and even, then opening his eyes to look to his Cloud guardian. Kyoya has his eyes closed, frowning darkly anyway, his whole posture tense, then he seems to instinctually pull against the vines keeping him on the ground. When that doesn't work, his eyes snap open and Tsuna can only see panic in the grey depths.  
Gone is the usual pride, the self confidence, the knowledge that all the world is begging for mercy on it's knees before his Cloud. When Tsuna looks into those grey eyes now, all he can see there is a primal terror.  
That strange protective feeling surges through him again, ten times as intense.   
Before Tsuna knows it, he has already approached the restrained Cloud, dropping to his knees before his guardian, so they are at the same level. 

Up close, it's even worse.  
Kyoya is so, so pale and his eyes are wide, unblinking. He seems to be blinded by this fear, not reacting to Tsuna's approach at all. There is a continuous shiver running its course through his body and his breath was beginning to come quicker.  
Tsuna reaches out, but one of the vines snaps out and wraps around his wrist, pulling his hand back down. Mukuro's voice is the only steady anchor point in a world that is falling to pieces. "Don't touch him. Tend to his flame, Bunny." 

Tsuna closes his eyes, taking a deep breath and reaching deep into himself, pulling at the core of his flame. It doesn't take much coaxing until the full force of it flows through his veins. Tsuna has already been determined to help.   
He pushes his flame outward, not to pierce, but to meet the Cloud flame that is trashing around the room. The primal fear is coming from it, that much is obvious, so Tsuna is kind of prepared to be met with resistance.   
What he isn't prepared for, is the soft noise that rips out of his Cloud when he finally manages to brush up against the flame in a friendly enough manner. Kyoya just whimpered. 

Tsuna's eyes fly open in alarm and... Yeah. Kyoya is completely lost to this primal terror, panting softly by now, tears rolling down his cheeks rapidly. His pale cheeks are flushed and he's actually crying.  
And honestly, if it weren't for Mukuro being the voice of reason, Tsuna would've just sat, mesmerized into speechlessness yet again. "Tsunayoshi. Focus. _Please _."  
He snaps out of the morbid fascination, his resolve coming back into focus and he narrows his eyes, glaring mildly at the dusting of purple that fills the air all around them, before closing his eyes to concentrate once more. __

__Kyoya's flame is stubborn as ever, in addition to being particularly furious at being restrained, so Tsuna has to be firm about it.  
He pushes up against the flame, slowing the trashing down significantly. Then he slowly but surely works on soothing down this trashing beast.   
Tsuna loses track of time as he works, his own resolve unwavering as he soothes and calms and even pets the trashing Cloud flame. He mightve been at it for minutes, or hours, Tsuna doesn't know anymore.   
But... Somewhere in that time, Mukuro has ended up joining them on the floor, one hand rested on Tsuna's shoulder. Tsuna knows it's Mukuro besides him, because he can still hear the soft whimpering and occasional gasping breath from Kyoya right before him._ _

__It's pure luck that Kyoya's flame is just stubborn and playing hard to get instead of being entirely unwilling to harmonize at all. It would have taken immense effort to harmonize with any unwilling flame.  
And it would be downright impossible with a flame this much stronger than his own. Kyoya's flame is massive, dense and high in purity, entirely too much for one single person to handle on their own.   
Yet, usually, Kyoya handles it as easy as breathing. It's an honest to god wonder that this is the only problem Kyoya ever seems to have had in regards to his flames.   
Tsuna is developing a whole new level of respect for his Cloud guardian. And he's genuinely starting to wonder why the man chooses to return to him as his home? Tsuna may never know, but he sure is flattered... _ _

__Mukuro then moves his hand off of his shoulder, grabbing Tsuna's limp wrist. His voice is right up against Tsuna's ear, grounding, more than distracting, calm and neutral. "I think it's fine if you touch him now. That should help with the harmonizing, right?"  
Tsuna can only grunt, still very much focused on the purple flame he's trying to coax closer. He needs to get at its core, but if keeps twisting out of his grasp with a snarling little chirp, keeping to just the edges of his flames.   
Mukuro then moves his hand forward, pushing him to... To hold Kyoya's hand.  
Tsuna can hear the hitch in Kyoya's breath at the new touch, but... Kyoya isn't pulling away. In fact, his fingers twitch, then clench against Tsuna's. It's an awkward angel to hold hands, but it does push the cloud flame closer into his grasp. _ _

__So Tsuna grabs a hold of the Cloud flame, pushing his own Sky flame into it, finally able to reach its core and-  
And... There is a fracture on this gorgeous core.  
Tsuna frowns darkly, brushing gently over the spiderweb-like cracks and hearing one of the whimpers tip over into a soft sob. He coos softly in response, an instinctual reply, apologetic. They were already harmonizing. _ _

__But why is a fracture here? Tsuna has never before noticed it, with how fine the cracks are. Usually, he would be harmonizing with Kyoya simultaneously as the others, otherwise, Kyoya's flame would be unwilling and flighty. It's just that right now he is hyper focusing on his Cloud, who was beginning to calm down slowly by the sounds of it,.  
It's not the first time they've harmonized, but it's the first time they have done so with just the two of them.   
Tsune isn't very familiar with flame core fractures, but he has felt them before. The first and last time he's felt one was on Reborn's core when they first began to harmonise. Reborn said that it is what happens when an element is betrayed by their sky or abandoned. A weak enough element would shatter outright and die. _ _

__What sky dared to abandon a Cloud this beautiful?  
Tsuna feels oddly annoyed and indignant, opening his eyes then and frowning slightly. Kyoya is finally calming down, blinking slightly, the dullness in his eyes slowly fading now. Kyoya's breathing was returning to normal levels and the tension melts out of his shoulders as if it was never there in the first place. The only traces left of what has happened are the vines still wrapped around him and the tear tracks down his cheeks.   
All the while, Mukuro was humming faintly besides them, sitting there, his hand still placed over both of theirs. Nobody seems to mind. _ _

__Kyoya blinks faintly at them, a little frown coming to his face easily enough. His voice is hoarse, but steady. Almost back to normal now. "What happened?"  
Tsuna pouts up at him, still holding his hand. "That's my question. Kyoya, why is there a fracture on your flame core? What bastard Sky abandoned you?"   
Kyoya doesn't make a move to pull his hand away, but he does huff faintly. "You won't like it if I tell you. And I mean that. It's best to move on."  
Mukuro cuts in, a nuisance as ever. "No, no more secrets, Birdie. Be honest."  
He's still holding onto both of their hands. Tsuna doesn't mind, he's busy pouting up at Kyoya and giving him his best puppy eyes. _ _

__Kyoya sighs softly, probably more agreeable due to the lingering effects of harmonizing just a minute ago. He looks Tsuna in the eyes, briefly considering his options, but he's restrained, holding hands and feeling way too relaxed to do just about anything. "Fine. It's you."  
Tsuna blinks rapidly at that, frowning more, genuinely confused. "What? How and when did that happen?"  
Kyoya shrugs mildly, but Mukuro reaches out and wipes some of the wetness off of his left cheek, giving him a reprimanding little pout. Two adorable pouts against one man with a weakness for the cute and soft. They aren't playing fair, but Kyoya can't find it in himself to care much at the moment. _ _

__He just sighs again. "We knew one another when we were very young. You probably don't remember anymore, neither do I really. It's been almost 20 years after all. I remember the time you were sealed however. That wasn't nice."  
Tsuna's eyes go big and wet, then he pounces forward and wraps his languid, relaxed Cloud in a fierce hug. Kyoya tenses slightly, but doesn't try to shove him off. He's kind of expected a reaction similar to this.  
The pitying look Mukuro gives him is much more annoying, so Kyoya wraps one hand into one of the loose vines around himself._ _

__Kyoya snaps that vine out in an arch, trapping himself the Mist and pulling his fellow guardian close.  
Mukuro rolls his eyes, wrapping his arms around Tsuna and cooing down at their whiny sky. Tsuna is pouting quite fiercely now, squeezing Kyoya, until his mind catches up with him and he pulls back, blushing furiously as well as looking very frightened.   
Kyoya looks down at this stupid, stupid sky that keeps pulling him in no matter what Kyoya does to him.  
His longing must have been obvious somehow, because suddenly, Mukuro jerks him forward by the vine around his forehead, making his forehead collide painfully with Tsunayoshi's. _ _

__It completely ruins the nice moment and Tsuna pulls back further with a yelp. Kyoya hisses and reaches up to soothe his own forehead, all while Mukuro bursts out laughing, still wrapping the sky in his arms. It's familiar, it's sweet, it's home. And Kyoya really wants to kiss them both._ _

__That will have to wait for another day however, because right now he really wants the Mist to hurt.  
Tsuna gives off one of those very herbivorous shrieks when Kyoya effortlessly rips the vines, pulls his tonfa out of nowhere and pounces onto both of them._ _

**Author's Note:**

> Thanks for reading!
> 
> Kudos and comments are muffin motivators! Bye bye~! ❤️


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